1. Field of the Invention
The present invention relates a method for managing and reproducing subtitle data of a high-density optical disc.
2. Description of the Related Art
Recently, optical discs like DVDs (Digital Versatile Discs) as well as optical disc apparatuses like DVD recorders and DVD players for recording and reproducing data to and from such optical discs have been actively developed and commercialized. These optical discs are capable of storing large amounts of high-resolution video data and high-fidelity audio data.
Generally, a DVD stores main video data and graphic or text data sometimes generically referred to as subtitle data. Subtitle data is often thought of as text or caption data that may be represented as a bit-map image. However, because this type of subtitle data is image data, some standards such as ETSI EN 300 743 V1.2.1 of the European Video Broadcasting Standard define subtitle data as textual and/or graphical information to provide subtitle or graphs. In this disclosure, the term graphic data or graphic information will be used interchangeably with the term subtitle data to refer to textual and/or graphical information. In a DVD, the subtitle data, such as captions or a logo, is recorded in a format of image data and is synthesized with the main video data when reproduced. In other words, when reproducing the DVD, an optical disc reproduction apparatus like a DVD player reads the subtitle image data together with the main video data from the DVD and outputs them to an external display device like a television receiver so as to produce and display a synthesized picture.
Accordingly, a user can see the reproduced main video data, like picture images, and the subtitle data, like captions or a logo, at the same time via the external display device.
More recently, a high-density optical disc like a BD-ROM having a higher recording density than a conventional DVD has been proposed, and debates on the standardization of such a newly proposed high-density optical disc are taking place in the industry. For example, a method for recording and managing graphic or subtitle data of a BD-ROM in a format of image data, like bit map (BMP) data, and reproduction control information thereof has been recommended.
However, there has not yet been provided an adequate data structure or methods for managing the reproduction of the subtitle image data recorded on a BD-ROM. In order to expedite commercialization of a newly proposed high-density optical disc like a BD-ROM, not only a recording medium data structure and method for recording the data structure, but also an effective method for reproducing the subtitle data are required.